Loudspeaker



Dec. 27, 1938. G. s. CARBONNEAU 2,141949 LOUDSPEAKER Filed April 17, 1957 IN VENT OR.

ATTORNEYS. W

UNl'iED STATES ATENT 2,141,949 LoDsPEAKEa Gordon S. Carbonneau, Chicago, lil., assigner to Utah Radio Products Company, Chicago, Ill., a corporation of Illinois Application April 17, 1937, Serial No. 137,434

6 Claims. (Cl. 179-1155) This invention relates to loudspeakers, and is ber to which the outer edge of the cone is to be particularly concerned with a novel and improved attached is for this purpose provided with a numarrangement for centrally securing the cone, and ber .of openings registering with corresponding more specically the so-called spider, in a dyopenings in the outer mounting edge or flange namic or moving coil type loudspeaker, whereby of the cone. These openings are aligned and the setting-up of stresses in the cone, and parthe mounting flange of the cone is suitably ceticularly torsional stresses, is eliminated. mented in place and rmly secured to the ring- The various novel features and objects of the like frame member. In other words, the outer invention will be better understood from a disedge of the cone is in this stage of assembly fixed lo cussion of the di'iculties and drawbacks resultin position, while its inner or apex end carrying 10 ing from previously known mounting provisions, the voice coil is still free or floating. The voice as briefly outlined below. coil is properly positioned or set within the air The moving coil or voice coil of a dynamic loudgap- In CCOldaHCe With DleVOllSlY kllOWl speaker is secured to the inner or apex end of structures, the spider is secured to the magnet l; the cone, and must be disposed within the ancore by means of a screw projecting through a nular or ring-like air gap provided between the suitable opening in its center and threaded into usual shell-shaped magnet and the central cylina threaded hole in the magnet core. drical core, so as to be freely movable therein. Torsional stresses effective to the cone are now The open end, i. e., the outer edge of the cone,` inevitably introduced at the moment when the is attached to a ring-like frame. A flexible or screw is tightened in place, because this tighten- 20 resilient member, commonly called a spider and ing operation is of a twisting character. The consisting of an axially resilient disk, is periphscrew enters progressively into the threaded eraily attached to the cone near its inner or opening in the core and, accordingly, the spider apex end. This spider is centrally secured to is progressively tightened down with an advancthe magnet core in order to position the inner ing twisting force. Inasmuch as the spider is 25 end of the cone and the moving coil so that the attached to the cone, this twisting force is transcoil is properly and freely movably located withmitted to the latter, and the inner or apex end in the air gap. Voice currents traversing the of the cone is more or less displaced or twisted windings of the voice coil move this coil axially with regard to its iixed outer edge which is sewithin the air gap and thus vibrate the cone. cured in place on the ring-like frame member. 'I'he spider yields to these vibrations, inasmuch Torsional stresses are thus set up in the cone, and as it is axially resilient and, being attached in its operating response is impeded, as mentioned its center to the magnet core and peripherally before, with the danger that these stresses might to the inner end of the cone, maintains the cone shift the voice coil out of its proper center poand voice coil in properly aligned operating position. 35 sition. t may be possible to overcome to some extent It will be clear that the above described setthe drawbacks resulting from this mounting ting or mounting of the cone must be effected method by repeatedly subjecting the loud speaker preferably without introducing any stresses in to tests and resetting the spider mounting after 40 the cone. If such stresses are present, e. g., each test, until the proper position of the cone 40 torsional stresses due to somewhat twisted setand voice coil is established. This is, of course, ting of the cone between its outer edge and its a procedure which is incompatible with efficient inner or apex end, the permanent setting or cenmanufacturing requirements, while the torsional tering of the voice coil is endangered and the cone stresses cannot be entirely eliminated, simply cannot vibrate properly because its natural or because they are an inevitable result of the 45.

normal frequency response is impeded and the mounting method as such employing torsional reproduction of sound is accordingly more or less force for securing the spider in place. adversely affected. In accordance with the present invention, the The following considerations will indicate the principal object is directed toward wholly obvidifficulties which are in the way of properly setating the above noted drawbacks. Briefly stated, 50 ting or mounting the cone free of stresses in instead of employing a screw for securing the accordance with previously known structures. spider to the magnet core by a twisting or tor- Eiiicient manufacturing processes require that sional force, I apply means whereby only straightthe position of the outer end or edge of the cone line axial forces are exerted for this purpose. be fixed in advance. The ring-like frame mem- This means may take the form of a suitable stud provided on the magnet core and projecting from it in the form of a short shaft. The centrally apertured spider'is slipped over this shaft, and this operation positions the spider, voice coil, and cone preliminarily in place and facilitates the requisite assembly, spacing, setting and checking operations. After the voice coil is properly set or aligned in its place within the air gap, a suitable washer-like fastening member is driven down upon the shaft projecting from the magnet core, in a straight-line motion extending substantially in the direction of the core axis and in frictional engagement with the shaft, until it clamps the spider down firmly in its proper predetermined place. The spider is thus securely attached to the magnet core and maintains the proper position of the voice coil and of the cone without the possibility of setting up any torsional or twisting stresses. The voice coil is positioned correctly and freely movable within the air gap and can freely vibrate the cone incident to its axial motions, and the cone can properly respond without being impeded ,by any undesired tensions or stresses within its structure.

The above intimated objects and other objects and features of my invention which have not yet been specifically mentioned will be fully brought out in the following detailed description which is rendered below'with reference to the drawing. In the drawing:

Fig. 1 represents a plane rear view of a loudspeaker showing the arrangement of the frame, magnet, and the transformer feeding the voice coil;

Fig. 2 is a section along the line 2 2 in Fig. 1;

Fig. 3 illustrates a frictional view, on an enlarged scale, of a section through the magnet core and related parts taken along the line 3 3 in Fig. 2;

Fig. 4 represents a section analogous to the one shown in Fig. 3 to illustrate a certain detail part; and

Fig. 5 is a partial front plane view of the structure looking particularly at the mounted spider in the direction of the arrows 5 5 in Fig. 2.

Referring now to the drawing, wherein like parts are designated alike, numeral II indicates a generally ring-shaped frame having legs I2 and I3 which are suitably secured, e. g., by spotwelding, to the shell-shaped magnet I4, as is particularly indicated in Fig. 2. 'I'he frame II with its legs I2 and I3 thus forms a structural unit with the shell of the magnet I4. The transformer I5 is also attached to the magnet I4 in any convenient and approved manner, for example, by means of a plate I6 (Fig. 1) which may be spot-welded to oneA side of the shell I4 and having ears such as Il' and I8. The transformer I5 may be secured to this plate I6 by means of a simple pressed frame comprising the sides I 9 2Il 2! and extensions 22-23, the latter engaging the ears H IS, respectively, as shown in Fig. 1. The frame I 9 26-2I is held in place by bending the ears I'I and I8 in upward direction. If desired, the ears I'I and I8 may be soldered to the extensions 22 and 23 so as to secure the mounting of the transformer in a reliable manner, The plate I6 may also be provided with projections, such as 24 25, which may be used for any desired purpose, for example, for the purpose of securing wires in place.

The shell-shaped magnet I4 is provided with a cylindrical central core 3i! around which may be placed, in any convenient and desired manner, the windings 3|. The core 30 may be attached to the corresponding side of the magnet shell by a press lit, or in any other desired and approved manner. The core 30 extends thus through the shell-shaped magnet casing, as particularly indicated in Fig. 2, and projects through an opening in the other side thereof, in such a manner as to leave a small annular or ring-like space which constitutes the air gap. The voice coil 4I is disposed within this air gap so as to be freely movable therein. Numerals 32 and 33 indicate the usual insulating disks cr washers placed on opposite sides of the winding 35. At 34 is shown an insert secured to the field coil for the purpose of clearly defining therair gap between the magnet and the core.

The foregoing description covers merely a generally known assembly including the combination of a frame (II I2 I3), with a shellshaped magnet (I4) and a transformer (I5). These parts form a unit which is best shown in Fig. 2.

Secured to this unit is the vibratory member or cone 4I) carrying the voice coil 4I and the spider 42. The latter is attached to the neck 54 of the core 30, thus securing the inner or apex end of the cone 40 in place. The outer end of the cone is provided with a flange which is attached to the ring-like frame II at the place where the frame terminates in the flanged end 43.

Attention will now be called to a number of details so that the new structure and its functions are better understood.

The voice coil 4I is provided on a suitable tubular insulator 44 which is suitably fastened, i e. g., cemented to the neck 45 of the inner end 0f the cone 4I). The cone is annularly offset at 46 4'I in order to strengthen its vibratory structure, and its outer end terminates in an annular corrugated portion 48 from which extends the annular flange portion 49. This flange portion constitutes the outer edge of the cone and is provided with suitable openings, such as 5I, which register with corresponding openings in the ring-like frame member II, as clearly shown in the drawing. The cone is also annularly offset at 52 to form a shoulder for receiving the spider disk 42, As will be clearly seen, particularly from Figs. 3, 4, and 5, the spider 42 consists of a disk-like structure which is disposed peripherally in the cone at the annular offset 52 and comprises a central apertured portion 53 (Fig. 3) which registers with the neck 54 of the core 30. The material of the spider is suitably cut out so as to form ribs, such as indicated in Fig. 5 at 55 5 51 58, these ribs connecting the outer or peripheral rim of the spider with the central portion and thus providing a structure which is axially displaceable or resilient. Since this spider disk is peripherally attached to the annular offset 52 of the cone, it forms a part of the cone. Its purpose is to hold the cone and also the voice coil in properly aligned operating position.

It will be well to recall at this point of the description the spider mounting method known prior to my invention, namely, the use of a screw inserted through the central aperture in the spider and engaging a corresponding threaded opening in the core until the screw tightened the central portion of the spider in iirm engagement with the core. This tightening operation, which involves a twisting force, produces the torsional stresses in the cone, simply because the twisting force of the screw is transmitted through the spider to the cone and puts the spider as well as the cone more or less under detrimental tension or torsional stress.

In the structure forming the subject-matter of my invention, the application of a twisting force is unnecessary, and torsional Stresses and tensions effective to the `cone or spider are wholly eliminated. This is accomplished by the provision of a device comprising a shaft indicated at 16 projecting from a threaded portion 1I adapted to be screwed into a corresponding threaded opening 12 in the neck 54 of the core 3i?. The enlargement 13 provided intermediate of the shaft and the threaded portion engages a shoulder in the upper part of the threaded opening 12 for the purpose of rmly attaching the stud in place and aligning and backing it properly substantially along the line of the axis of the core 30. This stud and shaft has a twofold purpose, namely, to facilitate the assembly operations and to hold the spider, and with it the voice coil and the cone, in proper operating position, as will now be explained in detail.

The cone with its spider and voice coil is put in place and the projecting shaft 10 enters through the opening in the central portion 53 of the spider. The stud thus holds the spider and with it the inner end of the cone and the voice coil in a preliminary assembly position and facilitates the proper centering of the voice coil within the air gap by the use of suitable spacing means. The outer end or flange 49 of the cone is attached to the ring-like frame member at the place indicated at t3, thus fixing the outer end or edge of the cone in place. This attachment may be made by means of a suitable ring 60 of fibrous material which is cemented to the frame and holds the outer edge of the cone properly in position. The ring 66 is provided with holes in alignment with the corresponding apertures in the flange of the cone end in the frame. The cone being thus secured at its outer edge, and the voice coil being properly aligned in the air gap by spacers or the like, the central portion of the spider can now be secured in engagement with the neck of the lcore 35. This operation is described below particularly with reference to Figs. 4 and 5.

A compressible or deformable member, e. g., a convex washer 15, is first put on the protruding shaft 10, and a fastening element, e. g., a washer 16, is then driven down upon the shaft 10 by applying solely straight-line forces extending substantialy along the line of the axis of the core 30. The opening in the washer 16 is slightly smaller than the diameter of the shaft 10, and thus is in frictional engagement with the stud. The washer 16 is driven down upon the shaft until it ilattens out the Washer 15, clamping the central portion 53 of the spider rrnly in place in engagement with the flat face of the neck 54 of the cone 36. The completed engagement is shown in Fig. 3. Inasmuch as no twisting forces whatsoever are applied, it will be clear that no stresses of any kind can possibly be set up in the cone. Accordingly, the cone will properly vibrate and will render an .improved and more faithful reproduction of sounds throughout its operating range, and the voice coil will stay in proper central position in the air gap.

A protective device, e. g., a processed screen or any other desired protective appliance may be secured so as to cover the spider on the outside.

The washer 16 may be of a peripherally hexagonal form, as shown in the drawing, particularly in Fig. 5, for the purpose of permitting removal of the threaded stud and associated shaft 10, if it should become necessary to remove the cone for any reason, e. g., to readjust the spacing of the voice coil. A twisting force is in this case applied to the Washer 16 which is in firm frictional engagement with the shaft 10, and the device can thus be removed as a unit in the manner of a screw.

The compressible member 15, which may take the form of a convex washer, is used in order to secure a full attachment of the central portion of the spider in contact with the end of the core piece, even in case the washer 16 should show some inequalities or in case the force applied to it is not fully and accurately in line with the axis of the core. In other words, the compressible washer 15 clamps the central portion of the spider in an annular t, even should the Washer 16 be slightly tilted with respect tothe shaft 1U.

The convex washer 15 is of a deformable o-r compressible structure. Accordingly, if desired, a washer may be used which is made of a compressible material, such as rubber, lead, brous paper or the like.

The shaft 1i] is shown to be of a generally cylindrical form. If desired, it may be slightly tapered. It is also understood that the cross section of this shaft may assume any desired form; for example, it may be triangular or square. In that case, the opening in the washer 16 would have to be triangular or square and correspond generally to the shape of the shaft. The shaft 16 may also be provided with a groove, and the washer 16 may carry an opening having a projection to fit the groove so as to provide a keyed connection between the shaft and the washer 16. Any structure which fulfills the requirement of a friction lit or keyed t can take the place of the one shown and described.

If desired, the device may also be used 'without any washer, such as 15, or its equivalent, particu larly in cases where the spider is of relatively soft material or of unusual thickness. In such a case, the use of a separate equalizing device or washer is superiiuous, because the spider material itself would be yieldable and would provide the equalizing requirements.

Attention is also called to the possibility of ,employing a washer 16 which is undercut on the side facing the spider. Such an undercut washer would bite into the spider material and secure it properly and firmly in place. Known compression types of washers may also be used in place of the washer 16 if desired.

Electrical connections have not been shown or described because they do not form part of the invention. It is understood that the field winding and also the transformer may be connected in any desired and approved manner, these devices being included in the disclosure only for the sake of completeness.

The invention may be used in part or in its entirety in connection with apparatus other than the one shown for the sake of convenient description in general, in all such cases Where a resilient or vibratory or exible element such as a diaphragm or cone or the like is to be mounted centrally and peripherally without producing any torsional or lateral tension or stresses. It is in this connection broadly immaterial whether the element to be secured in this manner is of a at annular shape or constitutes a cone-like structure.

I have shown and described a specific embodiment of my invention, but it will be understood that I do not desire to be strictly limited to the precise structural details of the individual elements in carrying the invention into practical use, .because changes and modications are possible above and beyond those indicated. It should therefore be understood that all such changes and modifications are to be considered my invention, provided they fall within the scope and spirit of the appended claims wherein I have defined what I consider new and desire to have protected by Letters Patent of the United States.

I claim as my invention:

i. In a loudspeaker, the combination, with a magnetic structure including a central core, a sound reproducing device equipped with a moving coil surrounding the end of said core, and a exible centering member secured to said device, of means for securing said member to said core, said means comprising a stud threaded into said core and projecting through an opening in said member, and a washer having an opening therein slightly smaller than said stud, said Washer being pressed onto said stud and serving to clamp said member to the end of said core.

2. In a loudspeaker, the combination, with a magnetic structure including a central core, a sound reproducing device equipped with a mov ing coil surrounding the end of said core, and a flexible centering member secured to said device, of means for securing said member to said core, said means comprising a slightly tapered pin xed to said core and projecting from the end thereof 'through an opening in said member, and a perforated element having a press nt on said pin outside said member and serving to hold the latter to said core.

3. In a loudspeaker, the combination, with a magnetic structure including a central core, a sound reproducing device equipped with a moving coil surrounding the end of said core, and a flexible centering membersecured to said device, of means for securing said member to said core, said means comprising two separate parts, one

of said parts having a threaded portion entering a tapped opening in the end of said core and a smooth shank portion projecting through an opening in said member, the other of said parts being a perforated member which is permanently united to the rst part by forcing it onto the shank portion of said first part, where it functions to clamp the said member to saidcore and also as a means whereby the rst part may be unscrewed from the core.

4. In a loudspeaker, securing means for the flexible centering member as set forth in claim 2, characterized by the provision of a deformable washer on one side of the flexible member.

5. In a loudspeaker, securing means for the flexible centering member as set forth in claim 3, characterized by the provision of plane surfaces around the periphery of said perforated member which adapt it for the application of a wrench.

6. In the loudspeaker art, the method of assembling a moving coil type of sound reproducing cone equipped with a flexible centering member near the apex of the cone to a magnetic structure including a central core surrounded by an air gap for receiving the moving coil and an attached frame for securing the rim of the cone, which consists in providing a centering pin projecting from the end of said core, placing the cone assembly on the magnetic structure assembly with said centering pin passing through a central opening in said exible membei', thereby utilizing the said pin and member to properly locate the moving coil in said air gap, securing the rim of the cone to said frame, and

then pressing a perforated member onto said pin by force applied in a direction parallel to the axis of the pin, whereby said exible member is secured to said core and at the same time angular displacement of said member relative to the rim of said cone is avoided.

G. S. CARBONNEAU` 

